Field of the Invention
The present invention relates to a electrophotographic member, an intermediate transfer member for use in an electrophotographic color image forming apparatus such as an electrophotographic photocopying machine and printer, and an electrophotographic image forming apparatus.
Description of the Related Art
A certain full-color electrographic image forming apparatus employs an intermediate transfer method, in which four color toners (yellow, magenta, cyan and black) are sequentially superimposed on a electrophotographic member such as an intermediate transfer member and then transferred to a medium to be recorded such as paper in a lump. In order to achieve high quality image by the intermediate transfer method, it is important to improve the transfer of a toner image to a medium to be recorded with enhanced toner releasability on the surface of an intermediate transfer member.
Japanese Patent Application Laid-Open No. 2008-129481 discloses an invention of an image forming semiconducting member which has effects of reducing attachment of paper powder and toner to the surface of the outermost layer, suppressing bleeding from the interior of the outermost layer, preventing contamination of a photo conductor, and the like. According to the description of Japanese Patent Application Laid-Open No. 2008-129481, it is preferable to add a silicone compound having a reactive group to the outermost layer, the reactive group being capable of more rigidly fixing the releasable component to the coating.
In recent years, in transferring the toner image on an intermediate transfer member to a medium to be recorded (hereinafter also referred to as “secondary transfer”), the applied voltage (hereinafter also referred to as “secondary transfer voltage”) tends to be increased in order to meet the demand for speeding up the electrophotographic printing rate and to further improve the transfer efficiency of toner. The present inventors have found that the increased secondary transfer voltage causes a discharge phenomenon between the surface of an intermediate transfer member and a transfer roller, which gradually decomposes silicone compounds in the surface layer. In other words, it was found that the releasability of the surface of an intermediate transfer member may be chronologically changed due to the decomposition of the silicone compounds in the surface layer. Hereinafter the degradation mode of a electrophotographic member due to discharge is described as “discharge degradation”.
With reference to Japanese Patent Application Laid-Open No. 2008-129481, the present inventors investigated an intermediate transfer member including silicone compound chemically fixed to the binder resin in a surface layer. Consequently, it was found that an effect for suppressing a bleeding of the silicone compounds. However, when the silicone compounds existing in the surface of a surface layer or in the vicinity of the surface are decomposed by discharge degradation, the toner releasability of the surface of a surface layer is reduced. Furthermore, the silicone compound fixed to a binder resin with a covalent bonding, existing inside the surface layer is hardly moved to the surface. Consequently the reduced toner releasability at the surface hardly be recovered. It is therefore required to develop technology for recovering the toner releasability at the surface in order to make an intermediate transfer member for use for a longer period.